Preventing overheating in classrooms: a thermodynamic simulation study in Barcelona

ideadmin on 18 June 2025

Prevención del sobrecalentamiento en aulas: un estudio de simulación termodinámica en Barcelona

As climate change intensifies summer heatwaves, ensuring thermal comfort in educational buildings is becoming a top priority

Preventing overheating in classrooms: a thermodynamic simulation study in Barcelona

As climate change intensifies summer heatwaves, ensuring thermal comfort in educational buildings – particularly in Mediterranean cities like Barcelona – is becoming a top priority. In this post, we explore the results of a detailed thermodynamic simulation study assessing the risk of overheating in two classrooms of a primary school located in Barcelona.

The study was commissioned to understand how effectively a dedicated outdoor air system with an Air Halding Unit supplying a constant 14 °C, could maintain thermal comfort from May to September * with no additional zone thermostat controls or zone dampers. No optimisation of the thermal envelope was considered in the study.

* Schools shut in Spain from the end of June until September. However, for the simulations, July and August were included in the simulations, to have results under more challenging climate conditions. This was also done as the climate file is based on historical data. Currently, weather conditions that typically occurred in July now often occur in May.

Objectives of the Study

The simulation aimed to answer three key questions:

How many hours during summer school hours do classrooms exceed 27 °C, despite cooled air being supplied at 14 °C?
What is the optimal relationship between outdoor air temperature and supply air temperature to prevent both overheating and overcooling, with a lower limit of 14 °C for supply air?
How does solar exposure differ between east- and west-facing classrooms, and how does this impact thermal comfort?

Simulation Tools and Model

Software Used: Simulations were carried out using DesignBuilder with the EnergyPlus calculation engine.
Climate Data: The IWEC II weather file for Barcelona–Airport, developed by ASHRAE, was used, based on long-term hourly data.
Building Model: The model includes two identical classrooms—one facing east, the other west—located on the third floor of a school. The corridor between them runs north–south. Internal floors and walls were modelled as adiabatic.
Envelope Performance: Building envelope parameters meet the minimum requirements of Spain’s CTE HE1 code for Climate Zone C (Barcelona). Windows are double glazed (Ug = 1.80 W/m²K) with a visible transmittance of 79% and a solar factor of 59%. The external wall has U = 0.49 W/m²·K, the roof has U = 0.40 W/m²·K and air permeability is n50 = 3 ach.
Solar Shading: Each classroom includes external fixed shading devices with a 50% reduction factor, simulating expanded metal mesh (deployé).

Internal Conditions and HVAC Configuration

Occupancy and Internal Loads: Each classroom is 60 m², with 31 pupils and one adult teacher. Lighting and equipment are only active during teaching hours (Mon–Fri, 08:00–18:00), though lighting is off in summer.
Ventilation Strategy: A central AHU supplies 100% fresh air at a flow rate of 45 m³/h per person (1395 m³/h per classroom), with 79% sensible and 62% latent heat recovery efficiency.
Cooling System: A air-water heat pump cools water to 7 °C, which is supplied to the AHU cooling coil, cooling the supply air to a constant 14 °C during summer school hours. The simulations assume this is also the respective zone supply air temperature (which in practice will not be the case due to heat gains/losses in the ductwork). In May and September, a dual-setpoint strategy is used to reduce overcooling:
· Outdoor T < 16 °C → Supply air at 20 °C
· Outdoor T > 17 °C → Supply air at 14 °C

Comfort Criteria

Thermal comfort was evaluated using the following thresholds:

Too Cold: Operative temperature ≤ 22 °C
Optimum comfort range: 22 °C – 27 °C, with minimum RH = 30% and maximum RH = 60% @ 26 ºC
Too Hot: Operative temperature ≥ 27 °C

The analysis focused on school hours only, from May to September.

Key Results

External Climate Overview (08:00–18:00, Mon–Fri)

Minimum, average and maximum outdoor dry air temperatures for each of the months simulated are shown in the Figure below:

Overheating Risk – Summary (% of teaching hours > 27 °C)

The table below shows the overheating risk assessment for each classroom and month:

The East-facing classroom experienced overheating in July and September, principally due to morning solar gains. The West-facing classroom, by contrast, performed slightly better, with only 1% of overheating in September.

Overcooling Risk – Summary (% of teaching hours < 22 °C)

The table below shows the overcooling risk assessment for each classroom and month:

Slight overcooling was observed in May and September in the West classroom, highlighting the impact of delayed solar exposure in the morning. The following Figures show the results in graphic form for May, July and September.

Key Takeaways

The central HVAC system generally maintains comfort during most of the school hours across both classrooms, despite the absence of zone-level temperature control.
Orientation matters: The East classroom heats up faster in the morning, while the West classroom is more prone to overcooling early in the day, especially in shoulder seasons.
July presents the greatest overheating risk, with internal operative temperatures exceeding 27 °C in the East classroom during 7% of teaching hours, despite the 14 °C supply air.
Overcooling is avoided through a well-designed dual-setpoint strategy in May and September, where supply air is adjusted depending on outdoor temperature.
Accurate commissioning is essential. Given the centralised nature of the system, delivering the correct airflow and temperature to each classroom is critical to ensuring real-world performance matches the simulation.

Final Thoughts

This simulation underscores the importance thoughtful but simple HVAC control logic in preventing thermal discomfort in classrooms. In warm climates like Barcelona, small improvements in system design and control can make a significant difference in educational outcomes and energy efficiency, using simple controls. For space cooling with 100 % outdoor air systems in larger buildings with long ventilation duct runs, it’s important to consider pressure losses and heat gains as cool air moves through the ductwork, and how this may impact flow rates and air temperature at the supply air grilles in each classroom.

Although not included in the study, it’s also essential to include and optimise passive design strategies (thermal insulation, window specification, airtightness, external shading devices, external “cool colours” and reduction of internal heat gains) to improve thermal comfort and reduce energy consumption.

As we move toward more resilient and climate-adaptive buildings, this study provides a clear example of how digital tools like EnergyPlus and DesignBuilder can inform evidence-based design decisions.

McCartney residence, Passivhaus Classic home

ideadmin on 5 June 2025

Description The McCartney Residence is located in New Plymouth, on the North Island of New Zealand. The home was built by eHaus, a company established in 2010 by Jon Iliffe and Baden & Glenda Brown with the dream of creating a New Zealand owned and operated specialist design and construction company using PassivHaus build and …

McCartney residence, Passivhaus Classic home

Passivhaus Certification

Description

The McCartney Residence is located in New Plymouth, on the North Island of New Zealand. The home was built by eHaus, a company established in 2010 by Jon Iliffe and Baden & Glenda Brown with the dream of creating a New Zealand owned and operated specialist design and construction company using PassivHaus build and design principles.

The home was designed by architect Ross Bennett, with Passivhaus consultancy done by Maria Rei of eHaus, and Passivhaus Certification by Oliver Style of Praxis Resilient Buildings.

This single-story, detached family home has a treated floor area of 125 m² and was built using a lightweight timber frame system, and Gealan Eco Passivhaus certified PVC windows were used. SIGA membranes and tapes have been used for airtight layer.

The blower door test for this home achieved an excellent result of n50 = 0,4 air changes per hour (ACH).

Ventilation is provided by a Zehnder ComfoAir Q350 HRV unit with whole house balanced mechanical ventilation with heat recovery. A Panasonic split system is used for heating and cooling.

Links:

iPHa (Base de datos internacional de proyectos Passivhaus)

Year: 2025

Location: New Plymouth, Taranaki, New Zealand

Architecture: eHaus – Ross Bennett

Services provided by Praxis: Passivhaus Certification

Passivhaus Certification Class: Passivhaus Classic

Climate zone: Warm Temperate

Floor area: 125 m2

Thermal envelope area: 460 m2

Blower Door Result: 0,35 n50

Heating Demand: 19 kWh/m2·a

Cooling Demand: 0 kWh/m2·a

Primary Energy Renewable consumption (EPR): 46 kWh/m2·a

Final Energy consumption: 44 kWh/m2·a

Renewable energy generation: 0 kWh/m2·a

CO2eq emissions: 16 kg/m2·a

Residence in Blenheim: Passivhaus Plus home

ideadmin on 5 June 2025

Description This new residence is located in Blenheim, on the South Island of New Zealand, and the first to receive Passivhaus certification in Marlborough. The home was built by eHaus, designed by architect Vlada Acimovic, with Passivhaus consultancy by Maria Rei of eHaus. The project was certified to Passivhaus Plus by Oliver Style of Praxis …

Residence in Blenheim: Passivhaus Plus home

Passivhaus Certification

Description

This new residence is located in Blenheim, on the South Island of New Zealand, and the first to receive Passivhaus certification in Marlborough. The home was built by eHaus, designed by architect Vlada Acimovic, with Passivhaus consultancy by Maria Rei of eHaus. The project was certified to Passivhaus Plus by Oliver Style of Praxis Resilient Buildings.

This is a single-story, detached building with a treated floor area of 157 m², built with a lightweight timber frame system, and Gealan Eco Passivhaus certified PVC windows with low-e triple glazing. SIGA membranes and tapes have been used for airtight layer. The blower door test for this home achieved an excellent result of n50 = 0,5 air changes per hour (ACH).

Ventilation is provided by a Zehnder ComfoAir Q350 HRV unit with whole house balanced mechanical ventilation with heat recovery.

“Certification was valuable to me, since my career as a chartered accountant attached value to the distinction between registered and unregistered practitioners,” explains co-owner Steven Molotsky.

This is the third project to be certified by Praxis Resilient Buildings in New Zealand.

Link to The Press article: https://www.thepress.co.nz/home-property/350404895/why-were-swapping-1927-bungalow-passive-house

Pep – iPHA

Year: 2025

Location: Blenheim, Marlborough, New Zealand

Architecture: eHaus – Vlada Acimovic

Service provided by Praxis: Passivhaus Certification

Passivhaus Certification Class: Passivhaus Plus

Floor area [m2]: 157

Thermal envelope area: 577 m2

Blower Door result: 0,46 n50

Heating Demand: 12 kWh/m2·a

Cooling Demand: 1 kWh/m2·a

Primary Energy Renewable consumption (EPR): 31 kWh/m2·a

Final Energy consumption: 29 kWh/m2·a

Renewable energy generation: 55 kWh/m2·a

CO2eq emissions: 10 kg/m2·a

Pavelló Illa: Barcelona’s new sports hub looks good, keeps cool and saves energy

ideadmin on 16 May 2025

Pavelló Illa: Diseño Pasivo y Simulación Energética en la Barcelona Urbana

Located in the dense urban fabric of Barcelona, Pavelló Illa is a new sports centre that stands out for its sensitive integration into a complex context.

Pavelló Illa: Barcelona’s new sports hub looks good, keeps cool and saves energy

Located in the dense urban fabric of Barcelona, Pavelló Illa is a new sports centre that stands out for its sensitive integration into a complex context. Anna Noguera, who co-designed the building with AIA Arquitectura i Instal·lacions, describes the project’s guiding principles:

“Designed as a light, translucent volume nestled between local schools and the massive Illa Diagonal shopping complex, the building acts as a mediating element—functioning by day as a sunlit interior and by night as a luminous urban lantern.”

From the outset, the project has embraced passive energy design and materials with a low environmental footprint. The structural system combines steel with CLT (cross-laminated timber), offering multiple benefits: reduced embodied energy, a lower overall carbon footprint, and improved possibilities for future disassembly and material reuse. The use of an industrialised timber system not only streamlines construction but also aligns with circular economy principles.

Praxis Resilient Buildings contributed to the project through an in-depth thermodynamic simulation study with the DesignBuilder tool, using EnergyPlus for thermal and natural ventilation modelling and radiance. The goal was to assess and optimise the building’s environmental performance throughout the year.

Our work focused on:

Solar gain analysis on the translucent thermal envelope to inform shading strategies.
Natural ventilation performance, including airflow modelling, opening controls, and seasonal flow rates.
Summer overheating risk reduction through integrated passive measures.
Daylighting studies to balance visual comfort with energy performance.
The thermal impact of green façades and vegetated areas, contributing to both internal comfort and urban heat island mitigation.

This holistic approach has helped shape a sports facility that is not only architecturally responsive but also performs exceptionally well from an energy and comfort perspective—offering a replicable model for resilient and sustainable public architecture in urban environments.

The Health Risks of Noise and the Passivhaus Solution

ideadmin on 14 May 2025

Los riesgos del ruido para la salud y la solución Passivhaus

Noise pollution is an often-overlooked environmental hazard that has significant health implications.

The Health Risks of Noise and the Passivhaus Solution

Noise pollution is an often-overlooked environmental hazard that has significant health implications. Chronic exposure to high noise levels is linked to stress, cardiovascular diseases, sleep disturbances, and reduced cognitive function. In urban environments, residents frequently contend with traffic, construction, and industrial noise, which can lead to long-term health consequences.

Traditional buildings often fail to provide adequate acoustic insulation, allowing external noise to penetrate living spaces. Poorly sealed windows, insufficient wall insulation, and gaps in building envelopes contribute to heightened indoor noise levels, reducing occupant comfort and well-being.

Passivhaus buildings, designed for maximum energy efficiency and thermal comfort, also excel in acoustic performance. The high-performance envelopes, triple-glazed windows, and airtight construction work together to significantly reduce noise infiltration. Additionally, the use of controlled mechanical ventilation systems ensures fresh air circulation without the need for open windows, further minimizing external noise intrusion.

Studies have shown that residents of Passivhaus-certified homes experience lower stress levels and improved sleep quality due to the superior acoustic insulation. By mitigating environmental noise, these buildings contribute to better mental and physical health, aligning energy efficiency with occupant well-being. As cities grow noisier, the role of Passivhaus in providing peaceful, healthy indoor environments becomes increasingly vital.

The Truth About Heating and Cooling in Passivhaus Buildings

ideadmin on 16 April 2025

Los edificios Passivhaus SÍ requieren un sistema de calefacción y refrigeración: desmintiendo un mito común

The Truth About Heating and Cooling in Passivhaus Buildings

Casa 1922 - NordEst Arquitectura - Filippo Poli

Passivhaus buildings are often marketed as requiring no heating at all, but this is misleading. While it is true that Passivhaus buildings achieve an impressive 70% reduction in space heating demand compared to conventional buildings, they still require a small heating system to maintain comfort during the coldest days of the year.

One of the core requirements of Passivhaus certification is to ensure thermal comfort in all occupied spaces throughout the year. This means that even with high-performance insulation, airtight construction, and a mechanical ventilation system with heat recovery (MVHR), some form of supplementary heating is needed. This is particularly critical in spaces such as bathrooms, where occupants are most vulnerable to cold immediately after showering, when they are wet and not wearing clothes. A small heating element in these spaces ensures comfort and compliance with certification standards.

In warm climates, the idea that Passivhaus buildings do not require active cooling is equally misleading. Overheating can still occur, and certification explicitly requires mechanical cooling when the overheating frequency—defined as the percentage of time when indoor operative temperatures exceed 25ºC—exceeds 10% according to the PHPP calculations. Even in buildings where overheating frequency is between 5% and 10%, Praxis, as qualified Passivhaus certifiers, strongly recommends incorporating a small cooling system.

Several factors contribute to the need for cooling, even in well-designed Passivhaus buildings. Natural night ventilation, while beneficial, is not always a reliable solution due to urban noise, security concerns, shading devices being closed at night, or the presence of insects. Additionally, urban heat island effects in cities lead to elevated ambient temperatures and reduced night-time cooling potential. Climate change further exacerbates this issue, with heat waves becoming more frequent and extreme, leading to sustained high indoor temperatures that can compromise comfort and health.

In summary, while Passivhaus buildings dramatically reduce energy consumption for heating and cooling, they are not completely independent of active climate control systems. A minimal heating system is necessary for year-round comfort, particularly in bathrooms, and a small cooling system is often essential in warm climates to prevent overheating. Properly understanding these requirements is crucial to ensuring that Passivhaus buildings provide the highest levels of comfort, energy efficiency, and occupant well-being.

Stairwell pressurization failing? A Blower Door test can help

ideadmin on 9 April 2025

¿Problemas con el sistema de sobrepresión de escaleras? Un ensayo Blower Door te puede ayudar

Stairwell pressurization systems are a fundamental component of fire safety in tertiary buildings.

Stairwell pressurization failing? A Blower Door test can help

Stairwell pressurization systems are a fundamental component of fire safety in tertiary buildings.

Their primary function is to keep the stairwell free of smoke in the event of a fire, ensuring a safe evacuation route for occupants and facilitating emergency services’ access. These systems operate by controlled air injection into the stairwell, creating a positive pressure that prevents smoke from entering from fire-affected areas. At the same time, the pressure can’t be so high, otherwise occupants will be unable to open doors to the stairwell, so typically air pressure needs to be maintained between 50 Pa and 60 Pa.

For the pressurization system to function effectively, it is essential that the stairwell and ventilation supply ducts have an adequate level of air tightness. If there are excessive air leaks through doors, joints, or poorly sealed construction elements or ventilation ducts, the pressurization fan may not reach the required pressure of 50 Pa, compromising the system’s effectiveness and endangering occupant safety.

To assess the air tightness of these spaces, at Praxis we have conducted a series of “Blower Door” air tightness tests in the stairwell of tertiary buildings such as offices and hospitals. The test is performed by installing a pressurization fan in one of the stairwell access doors and sealing the ventilation supply grilles on each floor. During the test, pressure differences are generated between the interior and exterior of the stairwell, allowing the measurement and detection of air infiltration. Once the course of leaks has been detected, they can then be corrected, to ensure that the pressurization system will achieve the required pressure values.

Thanks to our experience and technical expertise in air tightness testing, at Praxis we offer a specialized service to evaluate and improve the efficiency of pressurization systems in stairwells of tertiary buildings, thereby contributing to the safety and protection of occupants in emergency situations.

Mirador de Gracia: Catalonia’s 1st all-electric Passivhaus certified care home opens its doors

ideadmin on 12 March 2025

Mirador de Gracia: ¡la primera residencia de personas mayores 100% eléctrico de Cataluña abre sus puertas!

Mirador de Gracia, located in Barcelona, Spain, is the first Passivhaus certified care home in Catalonia,making itone of the most comfortable and energy-efficient care homes in the country.

Mirador de Gracia: Catalonia’s 1st all-electric Passivhaus certified care home opens its doors

Mirador de Gràcia, ubicada en Barcelona, España, es la primera residencia para personas mayores con certificación Passivhaus en Catalunya.

Mirador de Gracia, located in Barcelona, Spain, is the first Passivhaus certified care home in Catalonia, making it one of the most comfortable and energy-efficient care homes in the country.

The building was designed by Joaquim Rigau, Director General of FIATC Residencias, and developed by FIATC Residencias, as part of an investment programme of over 50 million euros with a capacity of more than 600 beds, 150 day-care places and more than 200 jobs across 5 new care homes in Barcelona, Viladecans, Vilanova, Alicante and Elche. All new FIATC care homes are in the process of Passivhaus certification.

Praxis Resilient Building has carried out the Passivhaus design and consultancy, PHPP calculations, thermodynamic and daylighting simulation, design of the thermal and airtight envelope, 2D and 3D thermal bridge calculations, HVAC systems consultancy, preliminary Blower Door tests and Passivhaus site supervision. Energiehaus Arquitectos were certifiers for the project.

Located in the Collserola hills with stunning views down to the sea and the port of Barcelona, Mirador de Gracia has a gross floor area of 6,692 m², distributed over eight floors with three co-living units adapted to the needs of the residents. 75 bedrooms provide a maximum capacity of 143 residents, with facilities such as a gym, pharmacy, industrial kitchen (with daily production of around 469 meals), laundry, hairdresser, seven sitting rooms and two roof gardens.

With a 59 kWp rooftop solar PV installation, this 100% electric building generates around 26% of its annual energy consumption, contributing to significant operational savings and reduction in CO² emissions. Heating, cooling and hot water production are provided by high-efficiency air-to-water heat pumps, eliminating the use of gas or other fossil fuel energy sources.

Given that care homes are power hungry buildings with strict thermal comfort requirements, the efficiency of the building will translate into a projected 70% reduction in energy costs compared to conventional care homes.

The FIATC Residencias technical team, with more than ten years of experience in the sector, has delivered the interior design, with all the furniture designed specifically to guarantee maximum comfort for both residents and staff working at the centre.

The fact that Mirador de Gracia is Passivhaus certified helps to maintain a stable indoor temperatures throughout the year, acoustic comfort to ensure rest, and good indoor air quality that helps reduce respiratory problems and improves quality of life and health for residents, while providing environmental and economic benefits through reduced energy consumption. Ultimately, the combination of efficient technologies and an optimized thermal envelope makes Mirador de Gracia a benchmark for sustainable architecture, demonstrating that well-being and sustainability go hand in hand.

Architectural design

Located in a privileged setting in the Collserola hills above Barcelona, Mirador de Gràcia has been designed to blend harmoniously into the landscape with a structure made up of two blocks of differing heights, allowing the creation of a large roof garden that connects the day areas and dining spaces, encouraging social interaction and enjoyment of the natural surroundings.

The architectural design is based on more than a decade of experience in managing nursing homes, with areas and furniture adapted to the needs of residents and staff. Priority has been given to creating warm and accessible interior environments, with 7 single rooms and 68 double rooms, all of which have natural light and exterior views.

Thermal envelope

The thermal envelope consists of 12cm of Sto EPS insulation on external walls, eliminating thermal bridges from the reinforced concrete structure. Additionally, there is 5cm of Knauf Insulation glass wool installed internally in the service void, manufactured with more than 80% recycled glass, with the E- Technology binder, which is plant-based and free of added phenols and formaldehydes, protecting both workers during construction and future occupants from harmful emissions.

The windows consist of Cortizo aluminium frames and low-emissivity and solar control glazing with argon gas, installed in wooden pre-frames and sealed with Ampack airtight tapes to eliminate air infiltration. Insulated EPS Cajaislant shutter boxes reduce heat loss from the external venetian blinds that provide automated shading for all windows and reduce cooling demands.

During the design phase, all construction details were studied and optimised to minimise or eliminate thermal bridges and eliminate cold spots.

10 preliminary Blower Door air tightness tests were done on the building, prior to the final test, with a result of n50 = 0.6 ren /h, making it one of the largest and most airtight buildings in Spain.

During the design phase, a series of thermodynamic and daylighting simulations were carried out using the DesignBuilder-EnergyPlus modelling tool, to optimise thermal performance and natural lighting. One of the objectives was to study the solar incidence on each façade and determine where low-e or solar control glazing would provide lowest heating and cooling demands and maximum daylighting. By reducing the glazing solar factor, the light transmission (natural light) and summer solar gains are reduced, with a consequent reduction in energy consumption from air conditioning; but free solar gains are also reduced in winter, with a consequent increase in heating energy consumption. The results of the study helped specify the glazing on each façade, finding a balance between daylighting and heating and cooling consumption.

Heating, cooling and hot water systems

Space heating and cooling is provided by 2 Hitachi Samurai air-to-water heat pumps (providing both heating and cooling) and 1 Hitachi Samurai chiller, with a total installed heating power of 488 kW and 507 kW of cooling power.

The heat pumps power indoor ducted fan coil units in the bedrooms and common areas, together with heating and cooling coils in the AHUs (air handling units), that warm or cool ventilation supply air, covering a part of the heating and cooling loads.

For DHW production, there are 5 Hitachi Yutaki air-to-water heat pumps, with two 1,000 litre hot water thermal storage tanks. DHW recirculation is controlled by the return temperature, to minimise heat losses in winter and internal heat gains in summer.

Sistemas de ventilación y renovación de aire

Ventilation and air renewal systems

The building has a highly energy-efficient balanced mechanical ventilation system with heat recovery, with 3 Passivhaus certified Swegon Gold RX air handling units that provide a maximum combined flow rate of 27,000 m³/h. The units have a sensitive heat recovery rate of 84%, with a maximum fan power consumption of 0.45 Wh/m³. Using the building’s control system, flow rates are adjusted according to occupancy. In the common areas, there are CO2 sensors that control motorized dampers, which open and close according to the concentration of CO2 and occupancy. Flow rates in bedrooms are regulated by time schedule, with CO2 sensors in a selection of rooms to monitor air quality.

The mechanical and electrical systems in the building were installed by Agefred.

All-electric industrial kitchen

The integration of an industrial kitchen in a Passivhaus care home is complex: equipment for food preparation, cooking and dishwashing consumes large amounts of energy and water, produces high internal heat gains (both latent and sensible), and requires high ventilation flow rates to remove contaminants.

Praxis undertook an extensive study in the design phase, to look at ways of eliminating gas-powered cooking equipment (generally the default in commercial kitchens and incompatible with the airtightness requirements of the Passivhaus standard) with efficient electrical equipment and dishwashers with low water consumption.

Peak kitchen hood extract air flow rates can sometimes reach ≈ 50% of the total ventilation flow rate that is required for the whole building. To this end, we specified an induction kitchen hood with a control system that modulates the air flow rate in the cooking area using temperature and smoke opacity sensors. In this way, the flow rate is adapted to cooking intensity, heat losses are greatly reduced, and fan electricity consumption can be reduced by up the 80%. The sensors are integrated into the induction hood and are easy to access and clean.

Renewable energy system

The building has a 59 kWp photovoltaic generator installed on the roof, with 131 Longi 450 Wp polycrystalline panels, and three SMA Sunny Tripower inverters, with an efficiency of 98%.

Monitoring

The Building Management System (BMS) is used to monitor the building’s energy consumption and indoor air quality, providing a means of assessing the building’s performance and comparing it with PHPP predicted energy consumption.

Conclusion

Mirador de Gracia sets a new benchmark for sustainable, energy-efficient care homes in Spain. By combining cutting-edge Passive House design, all-electric operation, and renewable energy generation, it demonstrates how comfort, health, and sustainability can coexist. This pioneering project not only reduces energy costs and carbon emissions but also enhances the well-being of its residents, proving that the future of care homes can- and should- be both resilient and environmentally responsible.

Photographs: Praxis, Salva Lopez & Miriam Castells

What is a Blower Door airtightness test and how can it improve my building?

ideadmin on 20 February 2025

What is a Blower Door airtightness test and how can it improve my building?

Infiltra-exfiltra 02-Fuente-Building Science Corporation

What is a whole building Blower Door airtightness test?

A Blower Door test is used to measure the airtightness of a building by quantifying its air leakage. The test involves using a large fan, temporarily mounted in an exterior doorway or other such opening, to either pressurize or depressurize the building. Sensors then measure how much air leaks through the cracks, gaps, and joints in the building envelope, giving an accurate picture of how well the structure prevents uncontrolled air infiltration or exfiltration.

Additionally, various tools can be used to identify exactly where air leaks are occurring so they can be corrected and sealed: these include handheld (generally hot wire) anemometers, smoke generators, thermographic camaras, and (our favourite and most high-tech sensor) a large feather, taped to an extendable fibre-glass fishing rod for reaching inaccessible spots where leaks are otherwise difficult to detect.

ISO 9972:2015 “Thermal performance of buildings – Determination of air permeability of buildings – Fan pressurization method” is the international norm that establishes the procedure for going about doing a Blower Door test and taking the measurements, although national buildings codes and specific building certification systems (such as Passivhaus) sometimes include variations on the norm, or require a specific methodology for calculating the internal air volume.

The test results are typically expressed according to one of the two following metrics, that can be used to assess the airtightness of buildings consistently across different types and sizes:

n50: the number of air changes per hour of air leakage at a pressure difference of 50 Pascals (ACH₅₀), referenced to the internal air volume of the building. This is probably the most common airtightness metric used. How the internal air volume is calculated is of course fundamental to the n50 result and must be clearly stated in the test report. ISO 9972 requires that the gross internal dimensions should be used and that “In general, the interior dimensions should be used to calculate this volume […] The volume of the interior floors or walls should not be subtracted. The volume of the interior cavities of the building envelope must not be subtracted”. Passivhaus, in contrast, requires that suspended ceilings and service voids are deducted from the calculation.

qe50: with this metric the air leakage is expressed according to the thermal envelope area, in units of m3/h·m2 (the m2 being the envelope area that encloses the heated and/or cooled space of the building). Again, the envelope area calculation is fundamental to the qe50 result and how it’s been calculated needs to be stated in the test report. ISO 9972 states it should be calculated according to internal dimensions, whereas Passivhaus typically uses external envelope dimensions.

Test methods according to ISO 9972

The norm states that there 3 methods for testing the airtightness of a building. Here too, the method fundamentally influences the end result and needs to be clarified before the test and in the final test report.

The 3 methods and their differences can be found here:

	Method 1	Method 2	Method 3
*Classification of openings in the building*	*Building in use*	*Building envelope*	*Specific purpose*
Natural ventilation openings	Closed	Sealed	Closed, sealed, or open, as directed
Mechanical ventilation system openings (continuous use)	Sealed	Sealed	Closed, sealed, or open, as directed
Mechanical ventilation system openings (intermittent use)	Closed	Sealed	Closed, sealed, or open, as directed
Exterior windows, doors & hatches	Closed	Closed	Closed, sealed, or open, as directed
Openings not designed for ventilation	Closed	Sealed	Closed, sealed, or open, as directed

Feeling the pressure? The process of a Blower Door Test!

1. Preparation: All external doors, windows, and vents are closed, except for the doorway or window where the fan is mounted. All internal doors must be opened to allow for a consistent pressure throughout the building, that mustn’t exceed +/- 10 % in any part of the building. For larger and particularly tall buildings, fans are often required at two or more points in the building to make sure pressure is equalised, and to counteract wind and internal air movement due to buoyancy. It’s generally preferable to test early in the morning, when there tends to be less wind, and to locate the testing equipment in the lee side of the building, where it is more protected from wind.

2. Pressurisation/Depressurisation: The fan blows air into or out of the building, creating a controlled pressure difference (in “cruise mode” this will usually be 50 Pa) between the interior and exterior. This difference replicates typical outdoor conditions such as wind or temperature fluctuations. 50 Pa of pressure difference is roughly equivalent to a 30 km/h wind. ISO 9972 states you can test either by pressurise or depressurise for a valid test. Passivhaus certification requires that you do both, with the final result being the average of the two. This is because there may, in practice, be both infiltration and exfiltration occuring in a building, often at the same time: the buoyancy of relatively warm air makes it rise, causing exfiltration on the upper floors, and drawing air into the lower floors (infiltration).

3. Measurement: As the fan operates, sensors measure the airflow required to maintain the pressure difference, which directly correlates with the volume of air escaping through leaks in the building envelope. For the final test, ISO 9972 requires that measurements are taken at a minimum of 5 different pressure intervals, with no more than 10 Pa at each interval, going from a minimum of 10 Pa (or at least 5 times the baseline pressure), to a maximum pressure of over 50 Pa for residential buildings and 25 Pa for non-residential.

4. Data Analysis: the data collected during the test is analysed to calculate the building’s n50 or qe50 value, indicating the air changes per hour or flow rate per metre squared of envelope. A lower n50 or qe50 score indicates a more airtight building. Results can also be expressed in terms of ELA, or Effective Leakage Area, which is the area of a theoretical hole which would exhibit same leakage as the building’s actual holes at a 4 Pa pressure difference.

Advantages of conducting a Blower Door Test

1. Improved Energy Efficiency: A Blower Door test identifies the specific areas where air is escaping, allowing builders and homeowners to address leaks. By sealing these leaks, the building’s overall energy consumption can be significantly reduced, lowering heating and cooling costs and contributing to long-term energy savings. A high level of airtightness must always be accompanied by a controlled mechanical ventilation system.

2. Enhanced Indoor Air Quality (IAQ): Air leaks can allow pollutants, allergens, and even moisture to enter the building from the outside. These unwanted infiltrants can compromise indoor air quality, especially in urban or industrial areas. An airtight building ensures that ventilation systems can filter and supply fresh air as needed, rather than relying on uncontrolled air infiltration.

3. Increased thermal and acoustic comfort: Drafts from air leaks can create cold spots and temperature fluctuations, impacting the comfort of occupants. By reducing leaks, a Blower Door test helps create a more consistent indoor environment that remains comfortably warm in winter and cool in summer. Airtight buildings also tend to be quieter, as they prevent sound from traveling through cracks in the envelope.

4. Compliance with building standards and certifications: Many building standards and green certifications, such as Passivhaus, LEED, and BREEAM, require a Blower Door test as part of the building performance verification process. Achieving a high level of airtightness is essential for meeting these standards and can also contribute to increased property value and recognition in the market.

5. Moisture damage and durability of the building structure: Uncontrolled air leaks can allow moisture to enter, which can lead to condensation within walls or roofs. Over time, this moisture can cause mold growth, wood rot, and structural damage. A Blower Door test helps prevent these issues by ensuring that the building envelope is properly sealed against unwanted air and moisture.

Resultados ensayo 03-Fuente-Alvaro-Martinez

Conclusion

A Blower Door test is more than just a diagnostic tool; it’s an investment in the efficiency, comfort, and durability of a building. By identifying and sealing air leaks, building owners can enjoy lower energy bills, healthier indoor environments, and increased structural longevity. In addition, this test is an essential step for projects aiming to meet strict building standards and achieve sustainable certifications.

For anyone involved in the design, construction, or maintenance of high-performance buildings, a Blower Door test is an invaluable step in quality assurance. Whether it’s for new construction or retrofits, the benefits of knowing—and controlling—air movement in a building make this test a valuable asset in sustainable building practices.

A Passive House that consumes less than it says on the tin?

ideadmin on 20 February 2025

Wow! A Passivhaus that consumes less than predicted by the PHPP!. Olloki is a single-family home in Navarra, northern Spain, which I recently certified to Passivhaus Plus standard.

A Passive House that consumes less than it says on the tin?

Wow! A Passivhaus that consumes less than predicted by the PHPP!

Olloki is a single-family home in Navarra, northern Spain, which we recently certified to Passivhaus Plus standard.

Designed by Pedro Mariñelarena Albéniz of IM Arquitectos Urbanistas, the house is built with honeycomb brick walls with 18cm of external thermal insulation, and 20cm of insulation on the roof. Triple glazed low-e windows are shaded in the summer with venetian blinds that have variable slat angles, so the occupants can find the right balance between solar control and daylighting.

A Zehnder Group Ibérica ComfoAir Q350 HRV mechanical ventilation with heat recovery system guarantees good air quality and removes pollutants and excess moisture from the indoor environment. A Daikin air-source heat pump powers the underfloor heating system and produces hot water. A 7,2 kWp solar roof mounted PV array generates around 8.600 kWh/a.

The occupants are super happy with the comfort and air quality of the house

But perhaps one of the best things about this home (…at least from our point of view as Certifiers!), is that it actually consumes LESS than predicted in the PHPP (this is without calibrating the PHPP with measured temperature setpoints, occupation, outdoor climate data etc…).

Total energy consumption and solar PV generation PHPP vs. measured average 2022-2024

Let’s have a look at the data:

The PHPP calculation predicts the home will consume 6,294 kWh/a.
The average measured energy consumption between 2022-2024 is 5,825 kWh/a.

Awesome!

The PHPP calculation predicts the home will generate 8,614 kWh/a of solar PV energy.
The average measured PV generation between 2022-2024 is 8,867 kWh/a.

Doubly awesome!

In the words of the A-Team chief, John ‘Hannibal’ Smith:

“I love it when a plan comes together”

Total energy consumption and solar PV generation PHPP vs. measured average 2022-2024

Preventing overheating in classrooms: a thermodynamic simulation study in Barcelona

Objectives of the Study

Simulation Tools and Model

Internal Conditions and HVAC Configuration

Comfort Criteria

Key Results

Overheating Risk – Summary (% of teaching hours > 27 °C)

Overcooling Risk – Summary (% of teaching hours < 22 °C)

Key Takeaways

Final Thoughts

McCartney residence, Passivhaus Classic home

Passivhaus Certification

Description

Residence in Blenheim: Passivhaus Plus home

Passivhaus Certification

Description

Pavelló Illa: Barcelona’s new sports hub looks good, keeps cool and saves energy

The Health Risks of Noise and the Passivhaus Solution

The Truth About Heating and Cooling in Passivhaus Buildings

Stairwell pressurization failing? A Blower Door test can help

Stairwell pressurization systems are a fundamental component of fire safety in tertiary buildings.

Mirador de Gracia: Catalonia’s 1st all-electric Passivhaus certified care home opens its doors

Mirador de Gracia, located in Barcelona, Spain, is the first Passivhaus certified care home in Catalonia, making it one of the most comfortable and energy-efficient care homes in the country.

Architectural design

Thermal envelope

Heating, cooling and hot water systems

Ventilation and air renewal systems

All-electric industrial kitchen

Renewable energy system

Monitoring

Conclusion

What is a Blower Door airtightness test and how can it improve my building?

What is a whole building Blower Door airtightness test?

Test methods according to ISO 9972

Feeling the pressure? The process of a Blower Door Test!

Advantages of conducting a Blower Door Test

Conclusion

A Passive House that consumes less than it says on the tin?

Wow! A Passivhaus that consumes less than predicted by the PHPP!

Total energy consumption and solar PV generation PHPP vs. measured average 2022-2024

“I love it when a plan comes together”

Overheating Risk – Summary (% of teaching hours > 27 °C)

Overcooling Risk – Summary (% of teaching hours < 22 °C)